在已设置重力/碰撞/弹性的情况下在 Swift 中移动对象（UIView）

Question

我想快速创建一个正方形，从屏幕顶部开始，下降到屏幕底部并停留在那里。我还希望能够用手指将其拖动到顶部，并使其再次落到屏幕底部。关于如何做到这一点有什么建议吗？

我已经能够创建一个落向屏幕底部的正方形。我也可以用手指移动它。但问题是，每当我移动它时，方块就会停留在同一个地方。我移动它后，重力/碰撞/弹性似乎不起作用。我希望在我将手指从广场上抬起后它会掉落。请参阅下面的我的代码摘录。可能有一些简单的事情我错过了。任何提示将不胜感激。

import UIKit

class ViewController: UIViewController {

  var greenSquare: UIView?
  var redSquare:UIView?
  var animator: UIDynamicAnimator?

  override func viewDidLoad() {
    super.viewDidLoad()
    createFallingObject()

    func createFallingObject() {

     //remove square from superview
     redSquare?.removeFromSuperview()

     //create the shape
     var dimen = CGRect(x: 130,y: 25,width: 90,height: 90)
     redSquare = UIView(frame: dimen)
     redSquare?.backgroundColor = UIColor.red

     //then add to the screen
     self.view.addSubview(redSquare!)

     //Initialize the animator
     animator = UIDynamicAnimator(referenceView: self.view)

     //Add gravity to the squares
     let gravity = UIGravityBehavior(items: [redSquare!])
     let direction = CGVector(dx: 0.0, dy: 0.05)
     gravity.gravityDirection = direction

     //Collision
     let boundaries = UICollisionBehavior(items: [redSquare!])
     boundaries.translatesReferenceBoundsIntoBoundary = true

     //Elasticity
     let bounce = UIDynamicItemBehavior(items: [redSquare!])
     bounce.elasticity = 0.3



     // 1. create a gesture recognizer (tap gesture)
     let tapGesture = UITapGestureRecognizer(target: self, action: #selector(handleTap(sender:)))


     //add pan gesture Regcognizer to the red square
     let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(handlePan))
     redSquare?.addGestureRecognizer(panGestureRecognizer)


     animator?.addBehavior(boundaries)
     animator?.addBehavior(bounce)
     animator?.addBehavior(gravity)
    }

    //this method handle pan
    func handlePan(_ gestureRecognizer: UIPanGestureRecognizer) {
     if gestureRecognizer.state == .began || gestureRecognizer.state == .changed {

        let translation = gestureRecognizer.translation(in: self.view)
        // note: 'view' is optional and need to be unwrapped
        gestureRecognizer.view!.center = CGPoint(x: gestureRecognizer.view!.center.x + translation.x, y: gestureRecognizer.view!.center.y + translation.y)
        gestureRecognizer.setTranslation(CGPoint.zero, in: self.view)

        //redSquare?.frame.origin.x = translation.x
        //redSquare?.frame.origin.y = translation.y
     }
   }

   // 3. this method is called when a tap is recognized
   func handleTap(sender: UITapGestureRecognizer) {
    createFallingObject()
   }
}

Answer 1

您应该在平移手势开始时从

UIDynamicAnimator

中删除该项目，并在结束时将其添加回来。

当视图添加到动态动画师时，其位置应由动画师和动画师单独确定。从动画制作器中删除该项目将允许视图使用其框架正常定位。将其添加回动画师将导致动画师将其从当前状态恢复定位。

或者，如果您需要手动更新项目的位置（即不基于动画师的物理原理），您应该调用

animator.updateItem(usingCurrentState: myDynamicItem)

，其中

myDynamicItem

是您要更新的项目。

Answer 2

animator?.removeAllBehavior()

在平移手势例程中做到了这一点